<p>Writing-intensive courses can actually be spread across many departments. For example, MIT has courses (or “subjects” in MIT-jargon) in every department (“course” in MIT-jargon) which are designated as “communication intensive”, and each student must take at least two in humanities, arts, and/or social studies and at least two in his/her major to graduate.</p>
<p>As far as double majoring goes, math and most humanities and social studies subjects typically do not require very large numbers of courses, so double majoring is generally quite feasable, especially for a student who has already completed several frosh/soph-level math courses before frosh entry.</p>